Pancreatic Ductal Carcinoma

Multiplanar, multiphasic CT or MR

CT : Poorly marginated, hypodense mass with tendency to infiltrate posteriorly into retroperitoneum

• Strong tendency to obstruct pancreatic and common bile ducts, with abrupt ductal cutoff at site of obstruction

• Pancreatic parenchymal atrophy upstream from mass

• Soft tissue infiltration to involve adjacent vessels and organs (e.g., duodenum, bowel, stomach, and adrenals)

• Most common sites of distant metastatic disease are liver, peritoneum, and lungs

• Arterial involvement quantified as < 180° or ≥ 180° tumoral involvement of vessel circumference

• Venous involvement may involve abutment, encasement, narrowing, or occlusion

MR : Tumor conspicuous on T1WI, appearing low signal and juxtaposed against high-signal pancreatic parenchyma

• T2WI less useful, as tumors are isointense to pancreas

• Conspicuity on contrast-enhanced T1WI similar to CT, with tumors showing progressive delayed enhancement

Most common malignant tumor of exocrine pancreas and accounts for > 95% of pancreatic malignancies

Most common symptoms are jaundice, weight loss, abdominal pain, and back pain

• Often asymptomatic until late in course, particularly body/tail tumors that do not cause jaundice

Only potentially curative treatment is complete surgical resection with negative surgical margins

Only 15-20% of patients are candidates for surgery at presentation, with 5-year survival of ~ 20% after surgery

5-year survival rate is < 5% without surgery with median survival of 3.5 months

Pancreatic adenocarcinoma, pancreatic cancer

Malignancy arising from ductal epithelium of exocrine pancreas

Best diagnostic clue

• Poorly marginated, hypoenhancing mass with abrupt obstruction of pancreatic duct ± common bile duct

Location

• Head (60%), body (20%), diffuse (15%), tail (5%)

Size

• Variable; average size 2-3 cm

CT sensitivity for pancreatic cancer is excellent (~ 97%)

• Excellent modality for determining unresectability (positive predictive value for unresectability of 89-100%)

• Less effective in determining resectability, as only 60-91% of tumors judged to be resectable on CT are actually resectable at surgery

Poorly marginated, hypodense mass with tendency to infiltrate posteriorly into retroperitoneum

• Tumor most conspicuous in portal venous (~ 70 seconds) and pancreatic (~ 40 seconds) contrast phases

• ~5% of tumors are isodense to pancreas on all phases, requiring attention to secondary signs of tumor

• Tumor virtually never calcifies in absence of treatment

Secondary signs of tumor

• Strong tendency to obstruct pancreatic and common bile ducts with abrupt ductal cutoff at site of obstruction

• Pancreatic parenchymal atrophy upstream from mass

• Abnormal contour of pancreas with loss of normal fatty lobulation and texture

• Soft tissue infiltration to involve adjacent vessels and organs (e.g., duodenum, bowel, stomach, and adrenals)

Distant metastatic disease

• Most common sites are liver, peritoneum, and lungs

• Regional lymph nodes frequently involved, but CT is not accurate for involvement (sensitivity < 20%)

• Adrenals, bones, and pleura (uncommon)

CT is best modality for determining vascular invasion

• Arterial involvement quantified as < 180° or ≥ 180° tumoral involvement of vessel circumference

• Venous involvement determined based on degree of contact between tumor and vessel, and described as abutment, encasement, narrowing, or occlusion

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    Distinction between < 180° or ≥ 180° involvement of veins no longer as important with advent of venous reconstruction

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    SMV or splenic vein narrowing often results in mesenteric or gastroepiploic collateral veins

• Tumor thrombus in mesenteric veins very uncommon (much more common with neuroendocrine tumors)

Pancreatic adenocarcinoma classically causes hypercoagulability: Look for evidence of incidental pulmonary emboli or deep venous thrombosis

Normal pancreas

• Diffusely high signal intensity on T1WI (≥ liver)

• Parenchyma variable in signal on T2WI

• Pancreas enhances avidly and homogeneously on T1WI C+ (hyperintense to liver on arterial phase and isointense on delayed phase)

MR is particularly helpful in identifying small group of tumors that are isodense to normal pancreas on CT

Tumor conspicuous on T1WI, appearing low signal and juxtaposed against high-signal pancreatic parenchyma

• Atrophic pancreas upstream from tumor often abnormally low signal on T1WI

T2WI generally not useful for tumor detection, as tumors often isointense to pancreas

Conspicuity on T1WI C+ similar to CT, with hypovascular tumors often demonstrating progressive delayed enhancement

Tumors often demonstrate restricted diffusion with lower ADC values than adjacent normal pancreas

• DWI not helpful in differentiating tumors from other entities (such as autoimmune pancreatitis)

MRCP and T2WI can demonstrate abrupt cutoff and obstruction of pancreatic and common bile ducts

MR generally 2nd choice (behind CT) for evaluating vascular involvement

Hypoechoic mass with only minimal internal color Doppler flow vascularity

Biliary dilation and pancreatic ductal dilatation upstream from tumor

Endoscopic ultrasound: Similar to conventional ultrasound findings, with inferior accuracy compared to CECT for locoregional staging or determining vascular involvement

• Helpful in excluding malignancy in patients with indeterminate CT findings (↑ negative predictive value)

• Can help guide biopsy of pancreatic masses

PET/CT

• PET alone (without diagnostic CT) is not effective for diagnosis of primary tumor (sensitivity as low as 72%)

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    Possible role in differentiating malignant from benign lesions, as FDG-avid lesions have ↑ risk of malignancy

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      May help differentiate pancreatic adenocarcinoma, which shows avid focal uptake in mass, from focal autoimmune pancreatitis, which shows diffuse uptake throughout pancreas and within salivary glands

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    Effective in judging response to treatment (chemoradiation), whereas CT may not differentiate posttreatment fibrosis from residual tumor

• PET not helpful for vascular involvement or locoregional staging (e.g., lymph nodes) due to poor spatial resolution

• Helpful for distant staging, and may change resectability status of ~ 20% of patients compared to CECT